Flame Tests Of Metal Cations

GPS : SC3-d , Students will relate light emission and the movement of the electrons to element identification.

Authors : Michala Metcalf and Olenkeya Irvin
Abstract : Perform flame tests of metal cations to observe their characteristic colors and match the colors observed to an appropriate wavelength of visible light.

Method :
Equipment :
  • 6 Wooden Splints (pre-soaked in distilled water)
  • Wash Bottle
  • Bunsen Burner
  • 250 ml beaker
  • 400 ml beaker
  • Distilled water
Solid Salts
  • LiCl
  • NaCl
  • KCl
  • CuCl2
  • BaCl2
  • CaCl2

Procedure :
  • Gather all equipment and chemicals.
  • Set up lab space.
  • Pour Distilled water into the 250 ml beaker and pre-soak the 6 wooden splints.
  • Light your Bunsen burner, then adjust the flame to a moderate temperature (no yellow in the flame)
  • Begin by dipping the end of a water soaked splint into one of the solid compounds. The solid crystals should coat the end of the splint.
  • Hold the coated end of the splint in the central portion, but just to the side of it, of the Bunsen burner flame.
  • Record the dominant color observed and its associated wavelength.
  • Repeat instruction 5-7 for the other 5 solids.

Dominant Color
Approximate Wavelength(in NM)*
Compound
Red
701
LiCl
Orange
609
CaCl2
Orange-Yellow
597
NaCl2
Yellow-Green
577
BaCl2
Green-Blue
492
CuCl2
Violet
423
KCl

Formulas : E = H x V (energy = plank's constant x frequency) H = 6.626 x 10 -34
V = C / λ ( frequency = velocity / wavelength) C = 3.00 x 10 10
nm = 10 -9m = 10 -7 m = 10 -5 cm


Calculations :
LiCl - V = (3.00 x 10 10) / (7.01 x 10 -5)
= .42796 x 10 15
= 4.28 x 10 14

E = (6.626 x 10 -34) x (4.28 x 10 14)
= 28.35928 x 10 -20
=2.84 x 10 -19

CaCl2 - V = (3.00 x 10 10) / ( 6.09 x 10 -5)
= .4926108374 x 10 15
= 4.93 x 10 14

E= (6.626 x 10 -34) x (4.93 x 10 14)
=32.66618 x 10 -20
= 3.27 x 10 -19

NaCl2 - V = (3.00 x 10 10) / (5.97 x 10-5)
=.5025125628 x 10 15
= 5.03 x 10 14

E = (6.626 x 10 -34) x (5.03 x 10 14)
= 33.32878 x 10 -20
= 3.33 x 10 -19

BaCl2 - V = (3.00 x 10 10) / (5.77 x 10 15)
= .5199306759 x 10 15
= 5.20 x 19 14

E = (6.626 x 10 -34) x (5.20 x 19 14)
= 34.4552 x 10 -20
= 3.45 x 10 -19

CuCl - V= (3.00 x 10 10) / (4.92 x 10 -5)
= .6097560976 x 10 15
= 6.10 x 10 14

E = (6.626 x 10 -34) x (6.10 x 10 14)
= 40.4186 x 10 -20
= 4.04 x 10 -19

KCl - V = (3.00 x 10 10) / (4.23 x 10 -5)
= 12.69 x 10 15
= 1.27 x 10 14

E = (6.626 x 10 -34) x (1.27 x 10 14)
= 8.41502 x 10 -20
= 8.42 x 10 -20

Error Analysis : There isn't a theoretical value to calculate the error .

Conclusion : Doing this lab let us find out the color and wave length the chemical produced. Each substances create a different level of energy produced. That means that every chemical will produce a different color in the flame test. The reason behind that would be because of the different energy levels. When an electron jump from one level to another and jump back; that shows the production of light.

Safety Precautions :
  • make sure hair is tied back
  • No jewelry
  • Closed toe shoes
  • Wear goggles
  • Wear aprons
  • Don't leave lab unattended